Glass substrates are used for various applications including automotive applications, architectural applications, aircraft applications, etc. Depending on the application, the glass substrate will need to exhibit certain performance properties such as visible light transmittance, infrared absorbance, etc. and aesthetic properties such as color, brightness, etc.
The performance properties of a glass substrate are primarily determined by the glass composition, i.e., the components used to make the glass. The glass composition is not the same as the batch materials (also referred to as the “starting materials”) that are processed by a standard glass making technique, such as float glass processing, sheet drawing processing, crucible melts, etc., to make the glass composition. Generally, a glass composition is made up of a base glass portion and a colorant portion. A base glass portion comprising SiO2, Na2O, CaO, MgO, Al2O3, and K2O is well known in the art. Glass having the aforementioned base glass composition is referred to as “soda-lime-silica” glass. Other types of known glass compositions include non-silicated glasses and silicated glasses such as alkali borosilicate glass, alkali free borosilicate glass, phosphate glass, alumino borosilicate glass, etc.
Oftentimes, a glass composition will contain one or more colorants that interact to provide a glass composition having the desired color. For example, cobalt, which is well known in the art as a blue colorant, can be mixed with cadmium selenide, which is well known in the art as a red colorant to provide a glass composition having a gray color.
Some glass compositions having a low redox ratio (definitions for redox terms are included below) have included nanostructure sized colorants. Such glass compositions are typically made by melting the batch materials, forming and casting the molten glass into a sheet and then further heating the glass sheet to cause the nanostructures to form. Because the batch materials must be melted and then further heat treated, the process for forming these glass compositions is inefficient and expensive.
The present invention provides a novel metal nanostructured colorant for high redox glass compositions (includes glass compositions that fall outside of the definition for “low redox”) such as, but not limited to, nanostructures of copper (Cu), gold (Au) and/or silver (Ag). Glass compositions according to the present invention are formed in a single heating step (i.e., the melting step).